let vm = new Vue({
    el: '#app',
    data:{
        firstname: 'Jean',
        lastname: 'DelaTour'
    },
    computed: {
        fullname: function() {
            console.log('cls called')
            return this.firstname + ' ' + this.lastname;
        },
        foo: function () {
            console.log('foo called')
        }
    }

});